Practicing should be fun and hunger for progress,just take it that way and you'll be fine,bpms will come as natural matter of things.I'm sure someone else would be able to give you more advices time wise,I never looked at the watch indeed.

After struggling with your Alternate Thirds exercise at first I am now 10 notes shy completing it at 100 BPM. Big milestone for me especially when I couldn't even do it at 30 BPM's about 3 weeks ago.

Concentrate playing it correctly. The speed will come naturally.But for arguments sake I recomend if your stuck at 95 bump to 105 and try to play it. You wont but when you get used to 105 going back down to 95 will seem slloooowwww.

Everything you learn try to practice with metronome. If you are bored to practice with metronome use some sort of Drum machine or Backing track. First determine tempo where you can easily play and then gradually increase the tempo by 4 to 8bpm. Try to play perfect whatever you are learning (chord sequence, lick , whole song/solo) at least 15 times in a row - but perfect. If you can do that , you are ready for the new tempo.

Yes, I've read that thread too, it was posted by Marcus Lavendell. It says that when practicing speed picking you psychologically need to get 'used' to speed. He recommends increasing speed even up to 300 bpm to feel the faster beat and try to follow that, even if you can barely follow it on one single string. After a while, turn it back to normal - this normal speed (e.g 100 bpm) will sound really slow.

My advice would be to sometimes do some bigger steps forward in speed. If your speed is around 100 bpm, you may go up to about 115-120, but not for long, just to reassure yourself about the target you want to achive, and then go back. This strategy is more about the psyche to open up yourself for speed. I've experienced that with 1 bpm increments it can get really dull and frustrating to speed up.

Ofc, you must remaing precise and surely speed will come after some hours of dedicated practice.

so i wonder how much i need to increase the bpm and for how long i should practise at the increased bpm for an improvment?

When you reach the point where you can't play the part perfectly, then stop and continue tomorrow from much low tempo again. This this when on the limit, increase bmp by only 1bpm per play. Repeat the exercise 5-10 times, if you do it cleanly and precisely, then you can push more. Also don't push it too far, and as soon as your hands start to get tired, stop and rest a bit, play some chords and move on.